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Elimination of Avalanche Injection in High Performance Field Effect Transistors

IP.com Disclosure Number: IPCOM000083536D
Original Publication Date: 1975-Jun-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Hornung, A: AUTHOR [+2]

Abstract

A basic problem affecting high-performance field-effect transistors is avalanche injection of hot electrons into the gate dielectric. It can be shown that the stability and performance of devices experiencing this problem will degrade to unacceptable levels.

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Elimination of Avalanche Injection in High Performance Field Effect Transistors

A basic problem affecting high-performance field-effect transistors is avalanche injection of hot electrons into the gate dielectric. It can be shown that the stability and performance of devices experiencing this problem will degrade to unacceptable levels.

The hot electrons are generated by high-electric fields in the drain-depletion region causing impact ionization and carrier multiplication, which leads to avalanche injection of electrons into the dielectric. These high fields in the depletion region can be reduced by increasing the thickness of the drain- depletion region.

In this technique, an extended graded junction in the drain-to-channel region is formed. This allows high-channel surface concentrations required to overcome "punch-through" on short channels, and at the same time reduces the electric field in the drain-depletion region to stop avalanching.

The extended graded junction can be achieved by either the technique shown in Fig. 1 or in Fig. 2. In Fig. 1, a masking layer 10 is deposited on wafer 12 and openings 14 and 16 made therein to define the source and drain regions, respectively. A thin oxide step 18 is provided adjacent the drain region opening
16. A single diffusion forms source region 20 and drain region 22. Underneath step 18 is formed an N-type region 24 having an impurity concentration less than the concentration in drain region 22.

An alternate technique...